The invention relates to hydrophilized polymers based on cellulose esters of aliphatic carboxylic acids. The hydrophilization according to the invention is carried out by impregnating the cellulose esters, where appropriate in the form of blends with ethylene/vinyl acetate copolymers in the solid phase or in a melt, with water-soluble vinyl monomers, and then polymerizing the vinyl monomers under the action of heat and/or light, where appropriate with the aid of radical initiators. The invention also relates to the use of hydrophilized materials of this type as biomedical materials in human or veterinary medicine, especially in ophthalmic contact optics.
A number of different hydrophilic polymers having water-absorbing capacities of 1 to about 60% by weight has already been employed in human medicine, for example as implants or as refractive materials in contact optics. In this connection, soft gels consisting of crosslinked (meth)acrylic acid oxyalkyl ester polymers or copolymers with vinylpyrrolidone, acrylic acid, methacrylic acid, acrylamide, methacrylamide or alkylsilyl esters of methacrylic acid, amongst others, are used. However, soft gels have the disadvantage that they can accumulate metabolites, infection-inducing substances and so forth, in their lattice. This has contributed to an increased use in contact optics of, instead of these soft gels, semihard materials of cellulose acetobutyrate or blends with ethylene/vinyl acetate copolymers (EVA) as is described, for example, in European Pat. No. 0,013,366. The water-absorbing capacity of cellulose esters or their blends with EVA is about 1 to 2%, depending on the content of free OH and the wettability with water is poor. To improve the compatibility with living tissue in the human biomedical sector, an improved wettability (in other words greater hydrophilicity) would be of great use. Since materials of this type are of particular interest for contact optics, it would be desirable if the materials also had at the same time high permeability to light.